Closed crankcase emission control systems require a high efficiency filter and crankcase pressure regulator. The high efficiency filter is required to filter out small sized particles to prevent contamination of the air, turbochargers, aftercooler, and internal engine components. The pressure regulator maintains acceptable levels of crankcase pressure.
In one example of the prior art, a pressure control assembly uses a diaphragm and a spring biasing means to maintain a constant vacuum in the system. The spring would cooperate with the diaphragm causing a valve within the diaphragm to move a variable orifice in order to maintain constant pressure. The problem with using a diaphragm and spring is that this type of system requires the use of a lot of small moving parts. The springs would eventually wear over time and need to be replaced before they failed.
In another example of the prior art, to make sure the vacuum in the crank case remains at a set negative pressure the valve member moves between at least fully closed, partially open and fully open positions. In a partially open position as compared to a fully open position the pressure drop between the points upstream of the valve to the point downstream of the valve is increased. The regulator chamber and an atmospheric chamber are formed in a housing. A diaphragm coupled to the housing, delimits the regulator chamber from the atmospheric chamber. The diaphragm and housing also delimit the atmospheric chamber which is opposite and below the regulator chamber. During operation, the positive atmospheric pressure in the atmospheric chamber can cause a plate and diaphragm and any weights to move upward, the movement causes the valve member to move up thereby placing the valve in a partially open or closed position from an open position or partially open position.